1. Field of the Invention
The present invention relates to a heat sink. More particularly, the present invention relates to a heat sink used for cooling an integrated circuit package, which generates heat, such as a microprocessor unit (MPU) incorporated into electronic equipment.
2. Description of the Related Art
Recently, concerning the integrated circuits used for a personal computer, especially concerning the MPU, the degree of integration is enhanced so as to enhance the function of the integrated circuit and increase the processing speed. Therefore, the quantity of heat generated in the integrated circuit has been increased. Accordingly, the inside of the casing of a personal computer is forcibly cooled by a cooling fan, and the MPU is located at a position where the cool air of the cooling fan flows, and a heat sink provided with a large number of fins is fixed to the MPU so that the MPU can be forcibly air-cooled. However, an MPU of a higher performance is now required for a personal computer. An MPU of a higher performance generates a quantity of heat larger than that generated by other electronic parts. For this reason, there is used a heat sink into which a cooling fan is incorporated so that an MPU, which generates a large quantity of heat, can be locally cooled by means of forcible air cooling. Such a heat sink into which a cooling fan is incorporated as a local cooling means is used to replace a conventional heat sink into which a cooling fan is not incorporated. Accordingly, there is proposed a heat sink of small size in which the cooling fan or a portion of the cooling fan is incorporated inside the cooling fins.
FIGS. 15Axcx9cC are views showing a heat sink described in Japanese Unexamined Patent Publication No. 62-49700 which is used as a local cooling means. FIG. 15A is a plan view which is taken from the upper surface side, FIG. 15B is a cross-sectional view taken at the one-dotted chain line ABCD shown in FIG. 15A, and FIG. 15C is a plan view taken in the direction of arrow Z in FIG. 15B. As shown in FIGS. 15A and 15B, this heat sink is composed in such a manner that a motor 2a, which is a drive section for blades 2b, is attached to the main body 1 of the heat sink, and fins 1a are perpendicularly arranged so that they surround the blades 2b. As shown in FIGS. 15B and 15C, the main body 1 of the heat sink is fixed to a heating element 3 such as a power transistor. Heat generated in the heating element is conducted to a bottom portion of the main body of the heat sink and further conducted to the fins 1a. When the motor 2a is driven, the blades 2b are rotated, so that cooling air is sucked from an upper portion of the cooling fan 2. The cooling air to which a centrifugal force is given by the rotation of the blades 2b cools the upper portions of the fins 1a, and the cooling air blown out downward by the blades 2b cools lower portions of the fins 1a. In this way, the cooling air which has been sucked from the upper portion passes through the fins 1a is discharged into the periphery of the heat sink. Therefore, the main body 1 of the heat sink can be cooled and further the heating element 3 can be cooled.
FIG. 16 is a view showing the heat sink described in Japanese Unexamined Patent Publication (PCT route) No. 8-502804. In the overall periphery of the main body 1 of the heat sink, there are provided a plurality of perpendicular fins 1a, and the cooling fan 2 is supported by the main body 1 of the heat sink. When the motor is arranged inside the blades 2b, the height of the cooling fan 2 in the axial direction is reduced, and when a portion of the cooling fan 2 intrudes into the main body of the heat sink, the thickness of the fan body 5 is reduced. When the cooling fan 2 is driven, the blades 2b are rotated, so that a cooling air can be sucked from the upper portion. The thus sucked cooling air cools the bottom portion of the main body 1 of the heat sink and passes through among the fins 1a. Therefore, the cooling air absorbs the heat which has been conducted from the main body 1 of the heat sink to the fins 1a, and the absorbed heat is dissipated to the periphery of the heat sink. When this heat sink is fixed to a heating element such as an MPU, the heating element can be locally cooled.
FIGS. 17A and 17B are views showing the heat sink described in Japanese Unexamined Patent Publication No. 6-268125. FIG. 17A is a plan view which is taken from the upper surface. FIG. 17B is a cross-sectional view taken on line Bxe2x80x94B in FIG. 17A. The motor 2a of the cooling fan 2 is fixed to the bottom portion of the main body 1 of the heat sink, and cooling fins 1a are perpendicularly arranged in such a manner that they surround the cooling fan 2. The bottom portion of the main body 1 of the thus composed heat sink is fixed to a heating element 3 such as an MPU. When the motor 2a is driven, the blades 2b are rotated, so that a cooling air can be sucked from the upper portion. The sucked cooling air passes through among the fins 1a and discharges into the periphery of the heat sink. When the fins 1a are cooled, the heating element 3 can be cooled via the main body 1 of the heat sink.
In the heat sinks shown in FIGS. 15A-C and 17A and 17B, the motor 2a which drives the cooling fan 2 is directly fixed to the bottom portion of the main body 1 of the heat sink. In the driving section of the cooling fan 2, ball bearings or sleeve bearings are used, and lubricant such as grease or oil is charged in the bearing. Due to the above structure, heat is directly transmitted to the bearing from the bottom portion of the main body 1 of the heat sink located close to the heating element 3. Accordingly, the temperature of the bearing is raised. When the temperature of the bearing is raised, the deterioration of the grease or oil is facilitated, and the life of the motor 2a is shortened.
In the heat sink shown in FIG. 16, the cooling fan 2 is mounted on the upper portion. Accordingly, areas of the fins 1a arranged on the side are small. Therefore, in order to realize a sufficiently high cooling performance, it is necessary to provide small fins with very small intervals between the fins. In order to realize the small fins 1a, the manufacturing cost is increased in the cutting process. Further, since the intervals between the fins 1a are very small, blocking tends to occur when dust gathers between the fins 1a. Accordingly, a quantity of cooling air is lowered, and the cooling performance is deteriorated.
In the structure of the heat sinks shown in FIGS. 15Axcx9cC and 17A and 17B in which the fins 1a are perpendicularly arranged on the overall bottom surface of the main body 1 of the heat sink, analysis of the flow of the cooling air becomes complicated and also analysis of the noise becomes complicated. Therefore, it is difficult to design the heat sink. Accordingly, it is impossible to optimize the cooling performance and reduce the noise.
It is an object of the present invention to provide a heat sink of low manufacturing cost and long life, the cooling performance of which is sufficiently high and in which the designing of the heat sink can be easily performed.
The invention described in claim 1 is to provide a heat sink comprising a box composed of a bottom surface coming into contact with a heating element, a side on which ventilation holes are formed and an upper surface on which a cooling fan having at least blades and a motor is embedded and fixed. Due to the above structure, when the design of the hole is changed, the performance can be easily optimized, and when the upper surface is provided on the box and the cooling fan is fixed onto the upper surface, the area of the side of the box can be sufficiently ensured, and further the deterioration of lubricant in the motor bearing can be prevented.
The invention described in FIG. 2 is to provide a heat sink in which the bottom surface is larger than a heat transmitting section coming into contact with the heating element, and ventilation holes are formed at positions on the bottom surface different from the position of the heat transmitting section. Due to the above structure, a change in the design of the hole can be performed in a wide range. Therefore, it becomes easy to optimize the performance. Further, the cooling performance can be enhanced and the noise generated by the cooling fan can be decreased.
The invention described in FIG. 3 is to provide a heat sink in which the ventilation holes formed on the bottom surface are open under the condition that the heat transmitting section comes into contact with the heating element. Due to the above structure, the quantity of cooling air passing through in the holes formed on the bottom surface of the box is increased, so that the performance of cooling the bottom surface of the box can be enhanced. Compared with a case in which holes are formed only on the side, the cooling air can flow smoothly. Therefore, the occurrence of noise can be decreased.
The invention described in FIG. 4 is to provide a heat sink comprising: a box composed of a bottom surface coming into contact with a heating element, a side on which ventilation holes are formed and an upper surface, the bottom surface having a heat transmitting section coming into contact with the heating element and also having ventilation holes; and a cooling fan composed of blades and a motor, wherein the cooling fan is embedded in the upper surface. When the upper surface is provided as described above, it is possible to ensure a sufficiently large area of the side which connects with the upper surface. Accordingly, the cooling performance can be enhanced. Further, it is possible to introduce a cooling air into the holes formed on the side and the bottom surface of the box. Therefore, the occurrence of noise can be decreased and the cooling performance can be enhanced.
The invention described in FIG. 5 is to provide a heat sink in which a radiating member is arranged between the cooling fan and the bottom surface of the box, and a portion of the radiating member is fixed onto the bottom surface. Due to the above structure, surface areas of the radiating fins are added to the surface area of the box. Therefore, the cooling performance can be enhanced.
The invention described in FIG. 6 is to provide a heat sink in which the dimensions of the box are larger than those of the heating element and are made to coincide with the outside dimensions of a socket holding the heating element, and the center of the cooling fan is located eccentric with respect to the center of the heating element. Due to the above structure, it is possible to fix the box to the socket. Even if the rotational center of the cooling fan is different from the heating center of the heating element, it is unnecessary to change the design of the holes on the side and also it is unnecessary to correct the design. Since the center of each component is different, it is possible to cool a portion of high temperature at the heating center by the strongest air flow sent out from the blades of the cooling fan. Accordingly, the cooling performance can be enhanced.
The invention described in FIG. 7 is to provide a heat sink comprising: a heat sink component having a bottom surface coming into contact with a heating element; a cooling fan having at least blades and a motor and a cover for fixing the fan to the heat sink component, wherein the cover is used for setting a distance so that a distance from the bottom surface of the cover at the end of the heat sink component to the upper surface of the heat sink component can be smaller than a distance from the bottom surface of the cover immediately below the fan to the upper surface of the heat sink component. Due to the above structure, it is possible to minimize the deterioration of the cooling performance without increasing the intensity of noise.
The invention described in FIG. 8 is to provide a heat sink comprising: a heat sink component having a bottom surface coming into contact with a heating element; a cooling fan having at least blades and a motor; and a cover for fixing the fan to the heat sink component, wherein the cover can be opened and closed round a hinge arranged at one end of the cover and locked at the other end. Due to the above structure, it is possible to conduct working on the heating element without removing the cover and the fan. That is, when the heat sink component to which the fan is attached is fixed to the heating element, it is possible to expose a hole for fixing the heat sink component by disengaging the lock of the cover and opening and closing it. Accordingly, it can be screwed and fixed there.
The invention described in FIG. 9 is to provide a heat sink comprising: a rectangular heat sink component having a bottom surface coming into contact with a heating element; a cooling fan having at least blades and a motor and a cover for fixing the fan to the heat sink component, wherein a heat conveyance member for diffusing heat is attached to the base of the heat sink component. Due to the above structure, the temperature at the end portion is not lowered, that is, the temperature of the overall heat sink can be made uniform. Accordingly, the cooling performance can be enhanced. The reason why the temperature of the overall heat sink can be made uniform is described as follows. In the case of a heat sink, the shape of which is rectangular, a quantity of heat transmitted in the longitudinal direction is decreased. Accordingly, the radiating efficiency of the heat sink is lowered at the end portion. However, according to the invention described in the claim, a heat conveyance member is arranged from the center of high temperature to the end in the longitudinal direction. Therefore, heat can be conveyed to the end portion of the heat sink.
The invention described in FIG. 10 is to provide an information processor comprising: a heat sink component having a bottom surface coming into contact with a heating element; a cooling fan having at least blades and a motor; and a cover for fixing the fan to the heat sink component, wherein a heat conveyance member is attached to the base of the heat sink component so as to convey heat to another cooling section. Due to the above structure, even if a quantity of heat generated by the heating element is increased, it is possible to incorporate the heat sink having the fan into the mounting space used presently. Up to this time, when the heat sink having the fan is incorporated into a limited mounting space, it is impossible to increase the volume of the heat sink and the capacity of the cooling fan in the case of an increase in the quantity of heat generated by the heating element when the processing speed is raised. However, according to the invention described in the claim, the heat conveyance member is arranged in the heat sink, and the increased heat is conveyed to another cooling unit by the heat conveyance member.
The invention described in FIG. 11 is to provide an information processor comprising: a heat sink component having a bottom surface coming into contact with a heating element; a heating element; and a printed circuit board, wherein the heat sink component and the cooling fan are fixed onto the printed circuit board by a bracket for fixing the heat sink having a cooling fan utilizing a hole for fixing the cooling fan. Due to the above structure, the hole for fixing the cooling fan is used. Therefore, while it is unnecessary to conduct an additional machining, the heat sink and the cooling fan can be attached to the printed circuit board of the apparatus. Accordingly, the occurrence of vibration and shock can be prevented at a low cost.